Asked  7 Months ago    Answers:  2   Viewed   33 times

Is there a better way than simply trying to open the file?

int exists(const char *fname)
{
    FILE *file;
    if ((file = fopen(fname, "r")))
    {
        fclose(file);
        return 1;
    }
    return 0;
}

 Answers

37

Look up the access() function, found in unistd.h. You can replace your function with

if( access( fname, F_OK ) == 0 ) {
    // file exists
} else {
    // file doesn't exist
}

You can also use R_OK, W_OK, and X_OK in place of F_OK to check for read permission, write permission, and execute permission (respectively) rather than existence, and you can OR any of them together (i.e. check for both read and write permission using R_OK|W_OK)

Update: Note that on Windows, you can't use W_OK to reliably test for write permission, since the access function does not take DACLs into account. access( fname, W_OK ) may return 0 (success) because the file does not have the read-only attribute set, but you still may not have permission to write to the file.

Tuesday, June 1, 2021
 
Noob_Programmer
answered 7 Months ago
53

Use boost::filesystem:

#include <boost/filesystem.hpp>

if ( !boost::filesystem::exists( "myfile.txt" ) )
{
  std::cout << "Can't find my file!" << std::endl;
}
Monday, June 28, 2021
 
jakubos
answered 6 Months ago
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